IGBT Modules - Technologies, Driver and Application (Second Edition) - page 513

Fig. 14.9
TC cycles of amodulewith a copper baseplate
With the PC test the module is actively heated and cooled for a certain number of
cycles. The heating is done by applying a load current, which leads to heating of the
junction of the semiconductor. Then the power is turned off and the system cooled down
quickly (e.g. by a water cooling turned on and off). The heating can be done in two
ways: Non-pulsed gate or pulsed gate. If the gate is not pulsed the power
semiconductor is switched on continuously. The losses emanate from the operating
current and the resulting saturation voltage U
. If the gate is pulsed, there will be
switching losses generated in addition, which will depend on the switching frequency.
The PC test with non-pulsed gate is much harder on the bond connections because
much higher currents are necessary in order to achieve the same losses. Unfortunately,
these important statements are missing in the manufacturer's PC diagrams. A closer
look at the test conditions should be used for any comparisons.
Essentially the PC so far is equivalent to the TC test with active heating. A difference,
however, is the cycle time. While in the TC test the cycle time is measured in minutes
(typically 5min), it only takes a few seconds (typically 3 seconds) in thePC test. For this
reason, the PC test is also known as PC
test and the TC test as a PC
Decisive criterion for the PC test is the saturation voltage U
or forward voltage U
The voltage is measured before the test as a reference. If during or after the test, a
change occurs outsidea defined area (e.g. +5%), the test is not passed.
Focus of test of the IGBTmodule is the bondwire connecting chip toDCB. Failures are
usually characterisedby the followingmechanisms:
Bondwire fracture
Lift-off of thebondwire from the chipmetallisation
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